From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1752289AbbKCLsP (ORCPT <rfc822;w@1wt.eu>);
	Tue, 3 Nov 2015 06:48:15 -0500
Received: from szxga02-in.huawei.com ([119.145.14.65]:51264 "EHLO
	szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1750852AbbKCLsK (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Tue, 3 Nov 2015 06:48:10 -0500
Subject: Re: [PATCH v2 27/32] scsi: hisi_sas: add smp protocol support
To: Arnd Bergmann <arnd@arndb.de>
References: <1445868903-183817-1-git-send-email-john.garry@huawei.com>
 <5633995D.20607@huawei.com> <5637977E.7000704@huawei.com>
 <4452058.YIXj3BxT1F@wuerfel>
CC: <mark.rutland@arm.com>, <devicetree@vger.kernel.org>,
        <linux-scsi@vger.kernel.org>, <pawel.moll@arm.com>,
        <ijc+devicetree@hellion.org.uk>, <JBottomley@odin.com>,
        <john.garry2@mail.dcu.ie>, <linux-kernel@vger.kernel.org>,
        <linuxarm@huawei.com>, <robh+dt@kernel.org>, <hare@suse.de>,
        <galak@codeaurora.org>, <zhangfei.gao@linaro.org>
From: John Garry <john.garry@huawei.com>
Message-ID: <56389DA6.6070103@huawei.com>
Date: Tue, 3 Nov 2015 11:42:30 +0000
User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:38.0) Gecko/20100101
 Thunderbird/38.2.0
MIME-Version: 1.0
In-Reply-To: <4452058.YIXj3BxT1F@wuerfel>
Content-Type: text/plain; charset="windows-1252"; format=flowed
Content-Transfer-Encoding: 7bit
X-Originating-IP: [10.202.137.251]
X-CFilter-Loop: Reflected
X-Mirapoint-Virus-RAPID-Raw: score=unknown(0),
	refid=str=0001.0A090201.56389EEA.0023,ss=1,re=0.000,fgs=0,
	ip=0.0.0.0,
	so=2013-06-18 04:22:30,
	dmn=2011-05-27 18:58:46
X-Mirapoint-Loop-Id: 8006d244ca6e653f7576d05b1914b158
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 02/11/2015 20:29, Arnd Bergmann wrote:
> On Monday 02 November 2015 17:03:58 John Garry wrote:
>>>
>>> Can do. Actually sg_req seems only ever has one element:
>>> expander.c, smp_execute_task()
>>> sg_init_one(&task->smp_task.smp_req, req, req_size);
>>>
>>>
>> I tried replacing with dma_map_single, but I feel the code is not as
>> clean as I need to manually set sg_dma_len() and sg_dma_address():
>>       req_len = sg_dma_len(sg_req) = sg_req->length;
>>       sg_dma_address(sg_req) = dma_map_single(dev, sg_virt(sg_req),
>>                                           req_len, DMA_TO_DEVICE);
>>       if (dma_mapping_error(dev, sg_dma_address(sg_req)))
>>            return -ENOMEM;
>> sg_dma_address(sg_req) is used in another function for unmap.
>>
>> opinion?
>>
>
> What I meant was not using a struct scatterlist at all:
> replace the 'sg_req' variable with a normal pointer, and then
> do
>
> 	hdr->cmd_table_addr = cpu_to_le64(dma_map_single(dev, req, len, DMA_TO_DEVICE));
>
> Any reason this won't work?
>
> 	Arnd
>
> .
>
There seems to be some misunderstanding. Are you suggesting I change 
sas_smp_task?
./include/scsi/libsas.h
struct sas_smp_task {
	struct scatterlist smp_req;
	struct scatterlist smp_resp;
};

thanks,
John